This application claims benefit of priority under 35 USC xc2xa7 119 to Japanese Patent Application No. 2000-29569, filed on Feb. 7, 2000, and Japanese Patent Application No. 2001-17405, filed on Jan. 25, 2001, the entire contents of which are incorporated by reference herein.
1. Field of the Invention
The present invention relates to a pressure-contact type semiconductor device, and more particularly relates to a pressure-contact type semiconductor device which is of a multiple chip module structure and includes a plurality of semiconductor elements. Further, the invention relates to technology which is applicable to a pressure-contact type semiconductor device for controlling vehicle motors, power sources and so on.
2. Description of the Related Art
A pressure-contact type semiconductor device used for power source control is mainly constituted by semiconductor elements such as insulating gate bipolar transistors (called xe2x80x9cIGBTxe2x80x9d) which function as a power device. In order to increase a current capacity, such a pressure-contact type semiconductor device employs a multiple chip module structure in which a plurality of semiconductor elements are electrically connected in parallel.
Referring to FIG. 12 of the accompanying drawings, a popular pressure-contact type semiconductor device 100 includes a plurality of semiconductor elements 103A to 103I arrayed in a circular pressure-contact type enclosure 101. Each of the semiconductor elements 103A to 103I is a semiconductor chip made of a single crystal substrate 103s as shown in FIG. 13. An IGBT is mounted on each semiconductor chip. Further, each of the semiconductor elements 103A to 103I is provided with an emitter electrode 103e and a gate electrode 103g on a front surface, and a collector electrode 103c on a rear surface.
Although not shown, the semiconductor elements 103A to 103I are arranged on a common collector electrode plate and include a common emitter electrode plate positioned thereon. The collector electrodes 103c are electrically connected to a collector electrode plate in order that a collector current flows from the collector electrode plate to the collector electrodes 103c. The emitter electrodes 103e are electrically connected to an emitter electrode plate in order to supply an emitter current to the emitter electrode plate.
The gate electrodes 103g are electrically connected to a gate terminal 104 provided at a part of the peripheral edge of the enclosure 101, using gate lead wires 105 extending in the enclosure 101.
In the foregoing pressure-contact type semiconductor device 100, distances between the gate electrodes 103g and the gate terminal 104 vary with the positions of the gate electrodes 103g in the enclosure 101, which means that the gate lead wires 105 have different lengths for connecting to the gate electrodes 103g. As a result, there are different wiring resistances and different inductances which would cause xe2x80x9ccurrent apportionment oscillation phenomenonxe2x80x9d and lead to malfunction of the pressure-contact type semiconductor device 100 when IGBTs are turn-off time.
The pressure-contact type semiconductor device 200 shown in FIG. 14 has been designed in order to overcome the technical problem of the semiconductor device 100 of FIG. 12, and is provided with the gate ring 106 around the inner peripheral edge of the enclosure 101. The sectional area of the gate ring 106 is larger than that of the gate lead wires 105. The gate ring 106 is partially electrically connected to the gate terminal 104. The gate electrodes 103g of the semiconductor elements 103A to 103I are electrically connected to the gate ring 106 using shortest gate lead wires 107 as possible. The gate ring 106 and gate lead wires 107 are connected using a Pbxe2x80x94Sn solder 108.
Further, Japanese Patent Laid-Open Publications No. 8-330338 and No. 9-321293 disclose the pressure-contact type semiconductor devices.
The pressure-contact type semiconductor device 200 of FIG. 14 seems to suffer from the following problems.
(1) The gate ring 106 has the sectional area which is larger than that of the gate lead wires 107, so that it has been expected that dispersion of the wiring resistances and inductances can be reduced. However, the gate electrodes 103g of the semiconductor elements 103A to 103I should be connected to the gate ring 106 using the gate lead wires 107. The lengths of the gate lead wires 107 vary with the positions of the semiconductor elements 103A to 103I. For instance, the length of the gate electrode 103g of the semiconductor element 103E at the center of the enclosure 101 is approximately twice the length of the gate lead wire 107 for the gate electrode 103g of the semiconductor element 103A near the peripheral edge of the enclosure 101. Therefore, it is very difficult to sufficiently reduce the dispersion of the wiring resistances and inductances in a gate voltage supplying path, and to reliably protect the pressure-contact type semiconductor device 200 against malfunction.
(2) The gate ring 106 and gate lead wires 107 are manually connected using the solder 108 but not automatically. Therefore, the pressure-contact type semiconductor device 200 is assembled with reduced workability, which would increase manufacturing cost and product cost.
(3) Further, the pressure-contact type semiconductor device 200 has a large current capacity and produces large calories, so that it is easily affected by heat or mechanical stress. Such stress concentrates on the solder 108 via which the gate ring 106 and gate lead wires 107 are connected, so that the solders 108 will be easily broken down or peel off.
(4) Still further, the pressure-contact type semiconductor device 200 includes many conductive components such as the gate ring 106 and gate lead wires 107, and many insulating films for insulating the conductive components, and so on. This not only complicates the structure of the semiconductor device but also increases manufacturing and product costs.
The invention has been contemplated in order to overcome the foregoing problems of the related art, and provides a pressure-contact type semiconductor device which can assure reliable circuit operation of a plurality of semiconductor elements, prevent malfunction and improve electrical reliability.
A further object of the invention is to provide a pressure-contact type semiconductor device which can be made compact by effectively using spaces between rows of semiconductor elements, in addition to the foregoing advantages.
It is a still further object of the invention to provide a pressure-contact type semiconductor device which can be efficiently and reliably assembled.
A final object of the invention is to provide a pressure-contact type semiconductor device which can reduce manufacturing and product costs through efficient and reliable assembling.
According to a first feature of the invention, there is provided a pressure-contact type semiconductor device comprising: a plurality of semiconductor elements each of which has a first main electrode and a control electrode positioned on a front surface and a second main electrode positioned on a rear surface; a second common main power source plate having the semiconductor elements on a front surface and electrically connected to the second main electrodes; a first common main power source plate arranged on the front surface of the semiconductor elements and electrically connected to the first main electrodes of the semiconductor elements; and a common control signal board arranged between rows of the semiconductor elements and electrically connected to the control electrodes of the semiconductor elements.
The semiconductor element is preferably an IGBT, a MOSFET (metal oxide semiconductor field effect transistor), a SIT (static induction transistor), a BJT (bipolar transistor), a SI thyristor (static induction thyristor), a GTO thyristor, an IEGT (injection enhanced gate transistor) and so on.
Specifically, the first main electrode is either an anode region or a cathode region in the SI thyristor or GTO thyristor, either an emitter region or a collector region in the BJT or IGBT, and either a source region or a drain region in the MOSFET or SIT. The second main electrode is either the anode or cathode region which does not function as the first main electrode in the SI thyristor or GTO thyristor, either the emitter or collector region which does not function as the first main electrode in the BJT or IGBT, and either the source or drain region which does not function as the first electrode in the MOSFET or SIT. In other words, in the SI thyristor or GTO thyristor, when the first main electrode is the anode region, the second main electrode is the cathode region. In the BJT or IGBT, when the first main electrode is the emitter region, the second main electrode is the collector region. In the MOSFET or SIT, when the first main electrode is the source region, the second main electrode is the drain region.
The control electrode denotes a gate electrode in the IGBT, MOSFET, SIT and so on while it denotes a base electrode in the BJT.
The common control signal board provides the control electrodes of the semiconductor elements with a control signal, and is made of at least a plate having appropriate rigidity, a thin flexible film or the like. The common control signal board is preferably provided between the rows of semiconductor elements without being in contact with them, i.e. the signal board is insulated from the semiconductor elements. Further, the common control signal board includes at least conductors, each of which has a cross sectional area larger than the cross sectional area of the gate lead wire of the pressure-contact type semiconductor device 100 shown in FIG. 12, or the cross sectional area of the gate lead wire 107 of the semiconductor device 200 shown in FIG. 14.
In the foregoing pressure-contact type semiconductor device, the common control signal board is in the shape of a mesh sheet and has electrode openings for the semiconductor elements.
The common control signal board extends substantially all over the spaces between the rows of semiconductor elements. This is effective in reducing and unifying wiring resistance and inductance in a route through which the control signal is transmitted. Therefore, it is possible to assure reliable operation of the semiconductor elements and reduce malfunction thereof, which enables the semiconductor device to be electrically reliable. Further, the pressure-contact type semiconductor device can be made compact by efficiently using the spaces between the rows of semiconductor elements for the common control signal board.
In accordance with a second feature of the invention, the common control signal board is a printed circuit board having insulating films and conductive films formed on the insulating films. The printed circuit board may be a multiple-layered printed circuit board in which the insulating films and conductive films are alternately layered. Therefore, the common control signal board is assembled in the semiconductor device as one unit. It is possible to reduce manufacturing and product costs of the pressure-contact type semiconductor device. Further, the control signal board is constituted by the insulating films and thin conductive films, and the insulating films can isolate the semiconductor elements, and the semiconductor elements from the thin conductive films, without using any additional insulating films. This is effective in reducing the number of components. Further, the insulating films and thin conductive films are integral and form a printed circuit board or a multi-layered printed circuit, which simplifies the internal structure of the pressure-contact type semiconductor device.
According to a third feature of the invention, the pressure-contact type semiconductor device further includes control signal probes for electrically connecting the thin conductive films of the common control signal board and the control electrodes of the semiconductor elements. The control signal probe and control electrodes are preferably in electric contact with one another.
The foregoing structure is effective in improving ease of assembly of the components and reliability of the assembling work. Especially, since no soldering work is performed, ease of assembly can be extensively improved and assembly work can be automatically carried out.
In accordance with a fourth feature, the foregoing pressure-contact type of semiconductor device further comprises a gate terminal for electrically connecting the thin conductive films of the common control signal board and an external device. The gate terminal has one end thereof connected to the external device and includes at the other end thereof a plurality of branched control signal leads electrically connected in parallel. The branched control signal leads are provided with pins for electrical connection with the thin conductive films of the common control signal board.
The branched common control leads of the gate terminal are effective in reducing the inductance. Further, the branched control signal leads are provided with a plurality of portions for connection with the common control signal boards. This structure is also effective in reducing the inductance and increasing a current capacity.